Micro-electro-mechanical system (MEMS) circuit and method for reconstructing an interference variable

Abstract

A Micro-Electro-Mechanical System (MEMS) circuit and a method for reconstructing an interference variable are provided. The MEMS circuit includes a MEMS device configured to generate a MEMS signal; a control circuit configured to detect a switched-on state or switched-off state of at least one device and configured to generate a control signal at least partly depending on the switched-on state or the switched-off state; a reconstruction filter configured to determine an interference signal that is partly generated by the at least one device, using the generated control signal; and a subtractor configured to subtract the determined interference signal from the MEMS signal.

What is claimed is: 
     
       1. A Micro Electro Mechanical System (MEMS) circuit, comprising:
 a MEMS device configured to generate a MEMS signal; 
 a control circuit configured to detect a switched-on state or switched-off state of at least one device thermally coupled to the MEMS device and configured to generate a control signal indicating the switched-on state or the switched-off state of the at least one device, wherein a temperature change in the at least one device causes the MEMS device to produce a corresponding thermal interference signal; 
 a reconstruction filter having an input coupled to the control circuit, the reconstruction filter configured to estimate the thermal interference signal in response to the generated control signal; and 
 a subtractor configured to subtract the estimated thermal interference signal from the MEMS signal. 
 
     
     
       2. The circuit as claimed in  claim 1 , wherein the control circuit is configured to generate the control signal upon the detection of the switched-on state of the at least one device. 
     
     
       3. The circuit as claimed in  claim 1 ,
 wherein the reconstruction filter comprises at least one amplifier; 
 wherein the reconstruction filter comprises at least one filter; and 
 wherein the filter is a second-order digital filter. 
 
     
     
       4. The circuit as claimed in  claim 3 ,
 wherein the amplifier is configured to receive the control signal of the control circuit and apply a gain to the control signal; 
 wherein the gain is adapted to the at least one device; and 
 wherein the amplifier is configured to generate the gain dependent on a power consumption of the at least one device. 
 
     
     
       5. The circuit as claimed in  claim 1 ,
 wherein the reconstruction filter furthermore comprises a high pass filter; and 
 wherein the high pass filter is a first order digital filter. 
 
     
     
       6. The circuit as claimed in  claim 1 ,
 wherein the reconstruction filter further comprises a digital adaptive filter; 
 wherein the adaptive filter is a finite impulse response filter (FIR filter); and 
 wherein the adaptive filter is a first order recursive filter. 
 
     
     
       7. The circuit as claimed in  claim 1 ,
 wherein the MEMS device is configured as a digital microphone; and 
 wherein the circuit furthermore comprises
 an amplifier, configured to amplify the MEMS signal, 
 an analog-to-digital converter configured to receive an analog output signal of the amplifier, 
 a digital low-pass filter configured to receive a digital output signal of the analog-to-digital converter, and 
 a modulator configured to receive an output signal of the subtractor. 
 
 
     
     
       8. The circuit as claimed in  claim 7 , wherein the output signal of the modulator is a 1-bit output. 
     
     
       9. The circuit as claimed in  claim 1 ,
 wherein the MEMS device is configured as a digital microphone; and 
 wherein the circuit furthermore comprises:
 an amplifier, configured to amplify the MEMS signal, 
 an analog-to-digital converter, configured to receive an analog output signal of the amplifier, 
 a digital low-pass filter, configured to receive a digital output signal of the analog-to-digital converter, and 
 a modulator, configured to receive an output signal of the digital low-pass filter and to provide it as the MEMS signal to the subtractor, 
 
 wherein the control circuit, the reconstruction filter and the subtractor are provided on a user-side electronic circuit that is external to the digital microphone. 
 
     
     
       10. The circuit as claimed in  claim 1 , wherein the MEMS device is configured as an analog microphone, and wherein the circuit furthermore comprises:
 an amplifier, configured to amplify the MEMS signal; and 
 an analog-to-digital converter, configured to receive an analog output signal of the amplifier and to provide the MEMS signal to the subtractor, wherein the control circuit, the reconstruction filter, the subtractor and the analog-to-digital converter are external to the analog microphone. 
 
     
     
       11. The circuit as claimed in  claim 1 , wherein the MEMS device is configured as a digital microphone, and wherein the circuit furthermore comprises:
 an amplifier, configured to amplify the MEMS signal; 
 an analog-to-digital converter, configured to receive an analog output signal of the amplifier; 
 a decimation filter, configured to receive a digital output signal of the analog-to-digital converter and to provide an output signal to the subtractor; and 
 an interface, configured to receive a result of the subtractor and to output a digital multi-bit signal. 
 
     
     
       12. The circuit as claimed in  claim 1 , wherein the device is at least one of a sensor, a microphone, a radio frequency amplifier, a power amplifier or an antenna of a telephone. 
     
     
       13. The circuit as claimed in  claim 1 , wherein the switched-on or switched-off state of the at least one device is configured to be received from a near environment and/or from a remote environment by the control circuit. 
     
     
       14. A method for reconstructing an interference variable, comprising:
 capturing a Micro Electro Mechanical System (MEMS) signal using a MEMS; 
 detecting a switched-on state or a switched-off state of at least one device thermally coupled to the MEMS device using a control circuit; 
 generating a control signal using the control circuit, wherein the control signal indicates the switched-on state or switched-off state of the at least one device, and a temperature change in the at least one device causes the MEMS device to produce a corresponding thermal interference signal; 
 estimating the thermal interference signal using a reconstruction filter in response to the generated control signal, wherein the estimated thermal interference signal models interference generated by at least one device; and 
 subtracting the estimated thermal interference signal from the MEMS signal. 
 
     
     
       15. The method as claimed in  claim 14 , wherein detecting the switched-on state or the switched-off state comprises detecting a state of at least one of a sensor, a microphone, a radio frequency amplifier, a power amplifier, or an antenna of a telephone. 
     
     
       16. The method as claimed in  claim 14 , wherein estimating the thermal interference signal comprises using a digital circuit. 
     
     
       17. The method as claimed in  claim 14 , wherein estimating the thermal interference signal further comprises capturing the switched-on state using the control circuit. 
     
     
       18. The method as claimed in  claim 14 , wherein estimating the thermal interference signal and subtracting the estimated thermal interference signal from the MEMS signal are performed externally on a user-side electronic circuit. 
     
     
       19. The method as claimed in  claim 14 , wherein estimating the thermal interference signal comprises using at least one amplifier; and
 wherein a gain factor of the at least one amplifier is set depending on a power consumption of the at least one device. 
 
     
     
       20. The method as claimed in  claim 14 , wherein estimating the thermal interference signal comprises using at least one filter. 
     
     
       21. The method as claimed in  claim 14 , wherein capturing a MEMS signal further comprises:
 amplifying the MEMS signal using an amplifier; 
 converting the amplified MEMS signal into a digital signal using an analog-to-digital converter; and 
 filtering the digital signal using a digital low-pass filter, 
 wherein subtracting comprises subtracting the estimated thermal interference signal from the filtered digital signal to form a result, and modulating the result using a modulator to produce a 1-bit signal. 
 
     
     
       22. The method as claimed in  claim 14 , wherein capturing a MEMS signal further comprises:
 amplifying the MEMS signal using an amplifier; 
 converting the amplified MEMS signal into a digital signal using an analog-to-digital converter to form the digital signal; 
 filtering the digital signal using a low-pass filter to form a filtered signal; 
 modulating the filtered signal using modulator to form a modulated signal; and 
 communicating the modulated signal externally to a user-side electronic circuit, 
 wherein subtracting comprises subtracting the estimated thermal interference signal from the modulated signal, and the subtracting is performed externally on the user-side electronic circuit. 
 
     
     
       23. The method as claimed in  claim 14 , wherein the method further comprises:
 amplifying the MEMS signal using an amplifier; 
 communicating the amplified signal externally to a user-side electronic circuit; and 
 converting the communicated amplified signal into a digital signal using an analog-to-digital converter externally on the user-side electronic circuit, wherein subtracting is performed externally on the user-side electronic circuit. 
 
     
     
       24. The method as claimed in  claim 14 , wherein the method further comprises:
 amplifying the MEMS signal using an amplifier; 
 converting the amplified MEMS signal into a digital signal using an analog-to-digital converter; and 
 reducing a sampling rate of the digital signal using a decimation filter to form a reduced sample rate signal, 
 wherein subtracting comprises subtracting the estimated thermal interference signal from the reduced sample rate signal and providing a subtraction result signal as a multi-bit signal via an interface.